1. Field of the Invention
The present invention relates to an optical scanning system, and more particularly, to an optical scanning system which allows spots of a light beam to land on a determined scan line at equal intervals.
2. Description of the Related Art
In an optical scanning system, non-linearity indicates that the spots of a light beam are formed on a scan line at irregular intervals. In the case where a light beam deflected by a rotary polygonal mirror of an optical scanner lands on a predetermined rectilinear scan line as spots, the distances between arbitrary positions on the scan line and the rotary center of the rotary polygonal mirror are different. Spots are formed on a rectilinear scan line at irregular intervals, by light beams sequentially reflected from the rotary polygonal mirror rotating at constant speed at constant angular intervals. As the spots move farther from the rotary polygonal mirror, on the basis of the spot formed on the scan line nearest the rotary polygonal mirror, the interval between the spots become wider. U.S. Pat. No. 5,117,243 discloses an optical scanning system for forming spots of a light beam on a rectilinear scan line at constant intervals.
The above optical scanning system controls the intervals of light beam emission having constant exposure time from a light source to form spots of the light beams on a scan line at equal intervals.
The optical scanning system controls a light beam for each pixel to maintain constant exposure time of the light beam, which makes it difficult to express the gray scale information with respect to a pixel.